If this flag is not set, then a callback is temporarily disabled, and should not be invoked.

See also

evbuffer_cb_set_flags(), evbuffer_cb_clear_flags()

If this flag is set, then we will not use evbuffer_peek(), evbuffer_remove(), evbuffer_remove_buffer(), and so on to read bytes from this buffer: we'll only take bytes out of this buffer by writing them to the network (as with evbuffer_write_atmost), by removing them without observing them (as with evbuffer_drain), or by copying them all out at once (as with evbuffer_add_buffer).

Using this option allows the implementation to use sendfile-based operations for evbuffer_add_file(); see that function for more information.

This flag is on by default for bufferevents that can take advantage of it; you should never actually need to set it on a bufferevent's output buffer.

Type definition for a callback that is invoked whenever data is added or removed from an evbuffer.

An evbuffer may have one or more callbacks set at a time. The order in which they are executed is undefined.

A callback function may add more callbacks, or remove itself from the list of callbacks, or add or remove data from the buffer. It may not remove another callback from the list.

If a callback adds or removes data from the buffer or from another buffer, this can cause a recursive invocation of your callback or other callbacks. If you ask for an infinite loop, you might just get one: watch out!

Parameters

buffer the buffer whose size has changed

info a structure describing how the buffer changed.

arg a pointer to user data

A cleanup function for a piece of memory added to an evbuffer by reference.

See also

evbuffer_add_reference()

Used to tell evbuffer_readln what kind of line-ending to look for.

Defines how to adjust an evbuffer_ptr by evbuffer_ptr_set()

See also

evbuffer_ptr_set()

Append data to the end of an evbuffer.

Parameters

buf the evbuffer to be appended to

data pointer to the beginning of the data buffer

datlen the number of bytes to be copied from the data buffer

Returns

0 on success, -1 on failure.

Move all data from one evbuffer into another evbuffer.

This is a destructive add. The data from one buffer moves into the other buffer. However, no unnecessary memory copies occur.

Parameters

outbuf the output buffer

inbuf the input buffer

Returns

0 if successful, or -1 if an error occurred

See also

evbuffer_remove_buffer()

Add a new callback to an evbuffer.

Subsequent calls to evbuffer_add_cb() add new callbacks. To remove this callback, call evbuffer_remove_cb or evbuffer_remove_cb_entry.

Parameters

buffer the evbuffer to be monitored

cb the callback function to invoke when the evbuffer is modified, or NULL to remove all callbacks.

cbarg an argument to be provided to the callback function

Returns

a handle to the callback on success, or NULL on failure.

Copy data from a file into the evbuffer for writing to a socket.

This function avoids unnecessary data copies between userland and kernel. If sendfile is available and the EVBUFFER_FLAG_DRAINS_TO_FD flag is set, it uses those functions. Otherwise, it tries to use mmap (or CreateFileMapping on Windows).

The function owns the resulting file descriptor and will close it when finished transferring data.

The results of using evbuffer_remove() or evbuffer_pullup() on evbuffers whose data was added using this function are undefined.

Parameters

outbuf the output buffer

fd the file descriptor

offset the offset from which to read data

length how much data to read

Returns

0 if successful, or -1 if an error occurred

Append a formatted string to the end of an evbuffer.

The string is formated as printf.

Parameters

buf the evbuffer that will be appended to

fmt a format string

... arguments that will be passed to printf(3)

Returns

The number of bytes added if successful, or -1 if an error occurred.

See also

evutil_printf(), evbuffer_add_vprintf()

Reference memory into an evbuffer without copying.

The memory needs to remain valid until all the added data has been read. This function keeps just a reference to the memory without actually incurring the overhead of a copy.

Parameters

outbuf the output buffer

data the memory to reference

datlen how memory to reference

cleanupfn callback to be invoked when the memory is no longer referenced by this evbuffer.

cleanupfn_arg optional argument to the cleanup callback

Returns

0 if successful, or -1 if an error occurred

Append a va_list formatted string to the end of an evbuffer.

Parameters

buf the evbuffer that will be appended to

fmt a format string

ap a varargs va_list argument array that will be passed to vprintf(3)

Returns

The number of bytes added if successful, or -1 if an error occurred.

Change the flags that are set for a callback on a buffer by removing some.

Parameters

buffer the evbuffer that the callback is watching.

cb the callback whose status we want to change.

flags EVBUFFER_CB_ENABLED to disable the callback.

Returns

0 on success, -1 on failure.

Change the flags that are set for a callback on a buffer by adding more.

Parameters

buffer the evbuffer that the callback is watching.

cb the callback whose status we want to change.

flags EVBUFFER_CB_ENABLED to re-enable the callback.

Returns

0 on success, -1 on failure.

Change the flags that are set for an evbuffer by removing some.

Parameters

buffer the evbuffer that the callback is watching.

cb the callback whose status we want to change.

flags One or more EVBUFFER_FLAG_* options

Returns

0 on success, -1 on failure.

Commits previously reserved space.

Commits some of the space previously reserved with evbuffer_reserve_space(). It then becomes available for reading.

This function may return an error if the pointer in the extents do not match those returned from evbuffer_reserve_space, or if data has been added to the buffer since the space was reserved.

If you want to commit less data than you got reserved space for, modify the iov_len pointer of the appropriate extent to a smaller value. Note that you may have received more space than you requested if it was available!

Parameters

buf the evbuffer in which to reserve space.

vec one or two extents returned by evbuffer_reserve_space.

n_vecs the number of extents.

Returns

0 on success, -1 on error

See also

evbuffer_reserve_space()

Read data from an evbuffer, and leave the buffer unchanged.

If more bytes are requested than are available in the evbuffer, we only extract as many bytes as were available.

Parameters

buf the evbuffer to be read from

data_out the destination buffer to store the result

datlen the maximum size of the destination buffer

Returns

the number of bytes read, or -1 if we can't drain the buffer.

Force all the callbacks on an evbuffer to be run, not immediately after the evbuffer is altered, but instead from inside the event loop.

This can be used to serialize all the callbacks to a single thread of execution.

Remove a specified number of bytes data from the beginning of an evbuffer.

Parameters

buf the evbuffer to be drained

len the number of bytes to drain from the beginning of the buffer

Returns

0 on success, -1 on failure.

Enable locking on an evbuffer so that it can safely be used by multiple threads at the same time.

NOTE: when locking is enabled, the lock will be held when callbacks are invoked. This could result in deadlock if you aren't careful. Plan accordingly!

Parameters

buf An evbuffer to make lockable.

lock A lock object, or NULL if we should allocate our own.

Returns

0 on success, -1 on failure.

Expands the available space in an evbuffer.

Expands the available space in the evbuffer to at least datlen, so that appending datlen additional bytes will not require any new allocations.

Parameters

buf the evbuffer to be expanded

datlen the new minimum length requirement

Returns

0 if successful, or -1 if an error occurred

Deallocate storage for an evbuffer.

Parameters

buf pointer to the evbuffer to be freed

Prevent calls that modify an evbuffer from succeeding.

A buffer may frozen at the front, at the back, or at both the front and the back.

If the front of a buffer is frozen, operations that drain data from the front of the buffer, or that prepend data to the buffer, will fail until it is unfrozen. If the back a buffer is frozen, operations that append data from the buffer will fail until it is unfrozen.

Parameters

buf The buffer to freeze

at_front If true, we freeze the front of the buffer. If false, we freeze the back.

Returns

0 on success, -1 on failure.

Returns the number of contiguous available bytes in the first buffer chain.

This is useful when processing data that might be split into multiple chains, or that might all be in the first chain. Calls to evbuffer_pullup() that cause reallocation and copying of data can thus be avoided.

Parameters

buf pointer to the evbuffer

Returns

0 if no data is available, otherwise the number of available bytes in the first buffer chain.

Returns the total number of bytes stored in the evbuffer.

Parameters

buf pointer to the evbuffer

Returns

the number of bytes stored in the evbuffer

Acquire the lock on an evbuffer.

Has no effect if locking was not enabled with evbuffer_enable_locking.

Allocate storage for a new evbuffer.

Returns

a pointer to a newly allocated evbuffer struct, or NULL if an error occurred

Function to peek at data inside an evbuffer without removing it or copying it out.

Pointers to the data are returned by filling the 'vec_out' array with pointers to one or more extents of data inside the buffer.

The total data in the extents that you get back may be more than you requested (if there is more data last extent than you asked for), or less (if you do not provide enough evbuffer_iovecs, or if the buffer does not have as much data as you asked to see).

Parameters

buffer the evbuffer to peek into,

len the number of bytes to try to peek. If len is negative, we will try to fill as much of vec_out as we can. If len is negative and vec_out is not provided, we return the number of evbuffer_iovecs that would be needed to get all the data in the buffer.

start_at an evbuffer_ptr indicating the point at which we should start looking for data. NULL means, "At the start of the buffer."

vec_out an array of evbuffer_iovec

n_vec the length of vec_out. If 0, we only count how many extents would be necessary to point to the requested amount of data.

Returns

The number of extents needed. This may be less than n_vec if we didn't need all the evbuffer_iovecs we were given, or more than n_vec if we would need more to return all the data that was requested.

Prepends data to the beginning of the evbuffer.

Parameters

buf the evbuffer to which to prepend data

data a pointer to the memory to prepend

size the number of bytes to prepend

Returns

0 if successful, or -1 otherwise

Prepends all data from the src evbuffer to the beginning of the dst evbuffer.

Parameters

dst the evbuffer to which to prepend data

src the evbuffer to prepend; it will be emptied as a result

Returns

0 if successful, or -1 otherwise

Sets the search pointer in the buffer to position.

If evbuffer_ptr is not initialized. This function can only be called with EVBUFFER_PTR_SET.

Parameters

buffer the evbuffer to be search

ptr a pointer to a struct evbuffer_ptr

position the position at which to start the next search

how determines how the pointer should be manipulated.

Returns

0 on success or -1 otherwise

Makes the data at the beginning of an evbuffer contiguous.

Parameters

buf the evbuffer to make contiguous

size the number of bytes to make contiguous, or -1 to make the entire buffer contiguous.

Returns

a pointer to the contiguous memory array

Read from a file descriptor and store the result in an evbuffer.

Parameters

buffer the evbuffer to store the result

fd the file descriptor to read from

howmuch the number of bytes to be read

Returns

the number of bytes read, or -1 if an error occurred

See also

evbuffer_write()

Read a single line from an evbuffer.

Reads a line terminated by an EOL as determined by the evbuffer_eol_style argument. Returns a newly allocated nul-terminated string; the caller must free the returned value. The EOL is not included in the returned string.

Parameters

buffer the evbuffer to read from

n_read_out if non-NULL, points to a size_t that is set to the number of characters in the returned string. This is useful for strings that can contain NUL characters.

eol_style the style of line-ending to use.

Returns

pointer to a single line, or NULL if an error occurred

Read data from an evbuffer and drain the bytes read.

If more bytes are requested than are available in the evbuffer, we only extract as many bytes as were available.

Parameters

buf the evbuffer to be read from

data the destination buffer to store the result

datlen the maximum size of the destination buffer

Returns

the number of bytes read, or -1 if we can't drain the buffer.

Read data from an evbuffer into another evbuffer, draining the bytes from the source buffer.

This function avoids copy operations to the extent possible.

If more bytes are requested than are available in src, the src buffer is drained completely.

Parameters

src the evbuffer to be read from

dst the destination evbuffer to store the result into

datlen the maximum numbers of bytes to transfer

Returns

the number of bytes read

Remove a callback from an evbuffer, given the function and argument used to add it.

Returns

0 if a callback was removed, or -1 if no matching callback was found.

Remove a callback from an evbuffer, given a handle returned from evbuffer_add_cb.

Calling this function invalidates the handle.

Returns

0 if a callback was removed, or -1 if no matching callback was found.

Reserves space in the last chain or chains of an evbuffer.

Makes space available in the last chain or chains of an evbuffer that can be arbitrarily written to by a user. The space does not become available for reading until it has been committed with evbuffer_commit_space().

The space is made available as one or more extents, represented by an initial pointer and a length. You can force the memory to be available as only one extent. Allowing more extents, however, makes the function more efficient.

Multiple subsequent calls to this function will make the same space available until evbuffer_commit_space() has been called.

It is an error to do anything that moves around the buffer's internal memory structures before committing the space.

NOTE: The code currently does not ever use more than two extents. This may change in future versions.

Parameters

buf the evbuffer in which to reserve space.

size how much space to make available, at minimum. The total length of the extents may be greater than the requested length.

vec an array of one or more evbuffer_iovec structures to hold pointers to the reserved extents of memory.

n_vec The length of the vec array. Must be at least 1; 2 is more efficient.

Returns

the number of provided extents, or -1 on error.

See also

evbuffer_commit_space()

Search for a string within an evbuffer.

Parameters

buffer the evbuffer to be searched

what the string to be searched for

len the length of the search string

start NULL or a pointer to a valid struct evbuffer_ptr.

Returns

a struct evbuffer_ptr whose 'pos' field has the offset of the first occurrence of the string in the buffer after 'start'. The 'pos' field of the result is -1 if the string was not found.

Search for an end-of-line string within an evbuffer.

Parameters

buffer the evbuffer to be searched

start NULL or a pointer to a valid struct evbuffer_ptr to start searching at.

eol_len_out If non-NULL, the pointed-to value will be set to the length of the end-of-line string.

eol_style The kind of EOL to look for; see evbuffer_readln() for more information

Returns

a struct evbuffer_ptr whose 'pos' field has the offset of the first occurrence EOL in the buffer after 'start'. The 'pos' field of the result is -1 if the string was not found.

Search for a string within part of an evbuffer.

Parameters

buffer the evbuffer to be searched

what the string to be searched for

len the length of the search string

start NULL or a pointer to a valid struct evbuffer_ptr that indicates where we should start searching.

end NULL or a pointer to a valid struct evbuffer_ptr that indicates where we should stop searching.

Returns

a struct evbuffer_ptr whose 'pos' field has the offset of the first occurrence of the string in the buffer after 'start'. The 'pos' field of the result is -1 if the string was not found.

Change the flags that are set for an evbuffer by adding more.

Parameters

buffer the evbuffer that the callback is watching.

cb the callback whose status we want to change.

flags One or more EVBUFFER_FLAG_* options

Returns

0 on success, -1 on failure.

Re-enable calls that modify an evbuffer.

Parameters

buf The buffer to un-freeze

at_front If true, we unfreeze the front of the buffer. If false, we unfreeze the back.

Returns

0 on success, -1 on failure.

Release the lock on an evbuffer.

Has no effect if locking was not enabled with evbuffer_enable_locking.

Write the contents of an evbuffer to a file descriptor.

The evbuffer will be drained after the bytes have been successfully written.

Parameters

buffer the evbuffer to be written and drained

fd the file descriptor to be written to

Returns

the number of bytes written, or -1 if an error occurred

See also

evbuffer_read()

Write some of the contents of an evbuffer to a file descriptor.

The evbuffer will be drained after the bytes have been successfully written.

Parameters

buffer the evbuffer to be written and drained

fd the file descriptor to be written to

howmuch the largest allowable number of bytes to write, or -1 to write as many bytes as we can.

Returns

the number of bytes written, or -1 if an error occurred

See also

evbuffer_read()